“I’ve got a bit of an irregularity with my heart that I have to keep on top of,” McIlroy told the Telegraph. “I have a flat T-wave and I’ll have to get an echo on my heart every six months and an MRI scan every year.”

McIlroy said the irregularity stems from a virus he got in 2016.

“I suffered a really bad viral infection in China 18 months ago,” McIlroy said. “They told me that’s the reason that I have this thickening of my left ventricle and there’s a bit of scar tissue. For now, I just need to stay on top of it and have to stay fit. Hey, I was planning on doing that anyway.”

McIlroy missed extensive time last season due to the rib injury and will return from a nearly four-month break next week at the Abu Dhabi Championship. He also shed light on some of last season’s struggles, during which he missed the cut at the U.S. Open and failed to contend at the PGA Championship at Quail Hollow, one of his favorite courses.

“To be honest, I just went through the motions for the last few months last year,” McIlroy said. “That’s not me. But it was a product of the circumstances. I knew within myself that I couldn’t compete at the end of last season because I hadn’t done the work beforehand, and that’s because I hadn’t been fit enough and if you can’t practice, you can’t compete.”

He regretted trying to play through injury at the U.S. Open and said he needed more time to recharge. He’s taken that time during his recent break and, having fallen to No. 11 in the Official World Golf Rankings, says he’s optimistic he can return to dominant form in 2018.

“I won four majors from 2011 to 2014 and everyone was saying, ‘That’s Tiger pace,’” McIlroy said. “Everyone knows I haven’t won one in the last three years and that is a worry, yeah. I need to get back on that track and this year my goals are to add to my major tally and get back to World No. 1, winning more times than anyone else.”